Abstract: Shu Xin San has good clinical efficacy. It can apparently inhibite platelet function and meanwhile improve erythrocyte surface charge. It is imply that Red Penoy Root in Shu Xin San play an important role in inhibiting platelet function. The reason of platelet aggregation depressed may be due to Red Peony Root raise the cAMP level of platelet. Red Penoy Root also can inhibite platelet aggregation initiated by TMVA （Trimeresurus macrosquamatus aggregoserpontin） and AA （Arachidonic Acid）, ADP, Adrenaline. It is suggest that Red Peony Root is a wide-spectrum inhibitor of platelet activation.